CVE-2020-1147
HIGHCVE-2020-1147 is a high-severity (CVSS 7.8) remote code execution vulnerability in Microsoft.NETCore.App. It is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) — treat it as actively exploited and patch now. O3 Security confirms whether CVE-2020-1147 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
.NET Framework, SharePoint Server, and Visual Studio Remote Code Execution Vulnerability
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2021-11-03. Federal agencies were required to remediate by 2022-05-03.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2020-1147.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2020-1147 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE sits: patch-first territory.
Where this sits among everything scored
Of 368,770 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
Microsoft.NETCore.App.NETMicrosoft.NETCore.App.Runtime.linux-arm.NETMicrosoft.NETCore.App.Runtime.linux-arm64.NETMicrosoft.NETCore.App.Runtime.linux-musl-arm64.NETMicrosoft.NETCore.App.Runtime.linux-musl-x64.NETMicrosoft.NETCore.App.Runtime.linux-x64.NETMicrosoft.NETCore.App.Runtime.osx-x64.NETMicrosoft.NETCore.App.Runtime.rhel.6-x64+4 moreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
A remote code execution vulnerability exists in .NET Framework, Microsoft SharePoint, and Visual Studio when the software fails to check the source markup of XML file input, aka '.NET Framework, SharePoint Server, and Visual Studio Remote Code Execution Vulnerability'.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.NETCore.App | ≥ 2.1.0&&< 2.1.20 | 2.1.20 |
| .NETNuGet | Microsoft.NETCore.App.Runtime.linux-arm | ≥ 3.1.0&&< 3.1.6 | 3.1.6 |
| .NETNuGet | Microsoft.NETCore.App.Runtime.linux-arm64 | ≥ 3.1.0&&< 3.1.6 | 3.1.6 |
| .NETNuGet | Microsoft.NETCore.App.Runtime.linux-musl-arm64 | ≥ 3.1.0&&< 3.1.6 | 3.1.6 |
| .NETNuGet | Microsoft.NETCore.App.Runtime.linux-musl-x64 | ≥ 3.1.0&&< 3.1.6 | 3.1.6 |
| .NETNuGet | Microsoft.NETCore.App.Runtime.linux-x64 | ≥ 3.1.0&&< 3.1.6 | 3.1.6 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Microsoft SharePoint Server 2019 - Remote Code Execution
by West Shepherd · Aug 17, 2020
Microsoft SharePoint Server 2019 - Remote Code Execution (2)
by Podalirius · Jul 23, 2021
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.NETCore.App. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update Microsoft.NETCore.App to 2.1.20 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-1147 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2020-1147 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2020-1147. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Frequently Asked Questions
Is CVE-2020-1147 in your dependencies?
O3 detects CVE-2020-1147 across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.